Seasonal abundance of Liriomyza sativae (Diptera: Agromyzidae) and its parasitoids on vegetables in Southern Vietnam

The vegetable leafminer Liriomyza sativae is an economically important pest of a wide variety of vegetable and ornamental crops in tropical Asian countries, but information on the relative abundance of the leafminer and its parasitoids is still limited. Field surveys were conducted through the year (from June 2005 to June 2006) in three commercial vegetable fields in Ho Chi Mirth City, southern Vietnam with the aim at monitoring the relative abundance of the leafminer and its parasitoids. Both adult and larva L. sativae were present in the vegetable fields throughout the year. The abundance of L. sativae on yardlong bean and kidney bean was relatively low in the beginning of growing seasons but the infestation became more serious in the end of the seasons. In contrast, the leafminer on cucumber and okra was highly abundant throughout the seasons. The abundance of parasitoids showed a similar tendency to that of the leafminer. The most frequent parasitoid species associating with L. sativae on yardlong bean, kidney bean and okra was Asecodes delucchii. Neochrysocharis beasleyi and N. formosa were common on garden cucumber and okra. The relative abundance of L. sativae and its associated parasitoids was influenced by seasonal climate, cropping schedules and pesticide applications. Hence, leafminer control strategies must be developed in a manner to conserve these parasitoid species by reducing the use of broad-spectrum insecticides and by applying some cultural control measures such as crop rotation and non-crop vegetation.